1. Field of the Invention
This invention pertains to a twisted conductor for the windings of electrical machines and devices, particularly transformers, which are assembled of single enamel-insulated flat partial conductors having a rectangular cross-section, in which the partial conductors on both flat sides of the cross-section extend obliquely in the opposite sense and, on the small sides of the cross-section, cross over, from one side to the other, via a sharp bend and wherein the stacked partial conductors, in cross-section, are arranged, next to each other with spacings.
2. Discussion of Background and Relevant Information
The use of twisted winding rods, so-called Roebel rods, in the production of electrical machines is known. Thus, these types of winding rods are used for the suppression or reduction of eddy current losses in the groove rods of particularly large electrical machines. In order to provide room for the axial through-put of a cooling medium, on the inside of the winding rod, that is, between the flat sides formed via the single conductors in the intermediate space between the two partial conductor stacks, specific cooling channels were formed through the corresponding arrangements of the partial conductors or specific formed conduits were arranged. For the strengthening of the winding rod it was provided with a glass-mica covering. This covering served, at the same time, as a cooling channel seal.
The utilization of twisted conductors as winding material in the manufacture of transformers has also been known for a long time. Moreover, twisted conductors are usually comprised of an uneven number of enamelled flat wires of copper or aluminum, that are stranded or roebelied according to a special system. During this process one conductor travels upwardly and one conductor travel downwardly regularly from one conductor stack to the other. The whole conductor bundle, depending upon requirements, is provided with a more or less thick paper insulation, wherein these paper wrappings on one side serve as additional insulation, depending upon the electrical strength, and on the other side are indispensable for the coherence of the conductor bundle. For additional stability of the bundle, a press board intermediate layer is longitudinally arranged between the conductor stacks.
During the winding of such twisted conductors, spacer platelets are inserted between the windings in order to form an oil channel for the improved cooling of the windings. These spacer platelets have a thickness of about 5 mm. Purely theoretically, this thickness could be reduced. Due to the paper insulation surrounding the twisted conductors however, this thickness must be chosen. This paper insulation however has the property that it, so to speak, loosens itself from the flat side of the twisted conductor and bulges into the cooling channel, thus reducing the cooling channel cross-section. In addition, in the region before and after the spacer platelets, cooling media jams are caused by the formation of pockets, thus resulting in poor cooling medium circulation.
From EP 167 896, a flanged spool winding for transformers is known. During this winding, spacer platelets are used for forming radial cooling channels. These spacer platelets are arranged between the windings and are manually inserted during the winding assembly. As a result thereof the previously recited disadvantages are accrued therefrom.
In addition, from EP 133 220, an electrical conductor with partial conductor transpositions, according to Roebel, is known, particularly wherein the conductor is stranded from six partial conductors, or elements. These elements are so arranged around a square pipe so that the square pipe serves as the cooling channel. In order to achieve increased coolant circulation the previously-discussed spacer platelets, with all their noted disadvantages, again had to be utilized.